JP2020095805A - Alkaline dry cell - Google Patents

Abstract

To achieve high capacity of an alkaline dry cell, while stabilizing explosion-proof function by the thin wall part of a gasket.SOLUTION: An alkaline dry cell includes a battery case having an opening, an electricity generation element received in the battery case, and a sealing unit for sealing the opening. The sealing unit includes a negative electrode terminal plate, a negative electrode collector joined to the negative electrode terminal plate, and a gasket. The gasket includes a boss part penetrating the negative electrode collector, periphery in contact with the end part of the opening in the battery case, and a coupling part for coupling the boss part and the periphery. A thin wall part having explosion-proof function is provided in the inner region adjoining the boss part of the coupling part, height of the boss part is 1.5-3.2 mm, and the difference φ1-φ2 of the first diameter φ1 of a circle drawn by the inside coupling position of the thin wall part and the boss part on the electricity generation element side, and the second diameter φ2 of a circle drawn by the outside coupling position of the thin wall part and the boss part in the negative electrode terminal plate side is 0.03-0.2 mm.SELECTED DRAWING: Figure 2

Description

The present invention relates to an alkaline dry battery, and more particularly to a structure of a sealing unit that seals an opening of a battery case.

The alkaline dry battery includes a battery case having an opening, a power generation element housed in the battery case, and a sealing unit that seals the opening of the battery case. The sealing unit includes a negative electrode terminal plate, a negative electrode current collector joined to the negative electrode terminal plate, and a gasket. The gasket includes a boss portion that allows the negative electrode current collector to pass therethrough, an outer peripheral portion that contacts the open end of the battery case, and a connecting portion that connects the boss portion and the outer peripheral portion. A thin-walled portion having an explosion-proof function is formed in an inner peripheral region adjacent to the boss portion of the connecting portion.

If the battery is misused, the internal pressure of the battery may rise abnormally. When the internal pressure of the battery rises abnormally, the connecting portion swells toward the negative electrode terminal plate, and the thin portion is ruptured by the tension applied. As a result, the gas generated in the battery is discharged to the outside of the battery through the gas vent hole formed in the negative electrode terminal plate. Therefore, the safety of the battery is ensured.

In order for the thin portion to break, a space is required for the connecting portion to expand toward the negative electrode terminal plate. However, when the battery temperature rises and the gasket softens when the battery is misused, the softened boss portion may be pushed up to the negative electrode terminal plate side against the frictional force with the negative electrode current collector. As a result, the distance between the connecting portion and the negative electrode terminal plate becomes short, the connecting portion cannot swell sufficiently, and it becomes difficult to break the thin portion.

Therefore, Patent Document 1 proposes that the difference between the inner diameter of the central portion of the boss portion and the minimum inner diameter of the upper and lower end portions of the boss portion is 0.03 mm or less. In this case, since the boss portion and the negative electrode current collector are firmly fitted to each other, the movement of the boss portion to the negative electrode terminal plate side is suppressed, and the explosion-proof function of the gasket is stabilized.

International Publication No. 2018-123123 Pamphlet

On the other hand, in the case of Patent Document 1, high molding accuracy is required for the boss portion, and therefore development of a gasket that is easier to manufacture and has a stable explosion-proof function is also desired.

One aspect of the present invention includes a battery case having an opening, a power generation element housed in the battery case, and a sealing unit for sealing the opening, the sealing unit including a negative electrode terminal plate and the negative electrode. A negative electrode current collector joined to the terminal plate; and a gasket, wherein the gasket has a boss portion through which the negative electrode current collector penetrates, an outer peripheral portion in contact with an opening end of the battery case, the boss portion and the A connecting portion that connects the outer peripheral portion, and an inner peripheral region adjacent to the boss portion of the connecting portion has a thin portion having an explosion-proof function, and the height of the boss portion is 1.5 mm or more, It is 3.2 mm or less and has a first diameter φ1 of a circle drawn by an inner connecting position of the thin portion and the boss portion on the power generating element side, and an outer side of the thin portion and the boss portion on the negative electrode terminal plate side. The present invention relates to an alkaline dry battery in which a difference between a second diameter φ2 of a circle drawn by connecting positions: φ1-φ2 is 0.03 mm or more and 0.2 mm or less.

According to the above aspect, the thin portion can be broken while the connecting portion appropriately bulges toward the negative electrode terminal plate, so that the stability of the explosion-proof function is improved.

It is a half cross-sectional view showing an example of an internal structure of an alkaline dry battery according to an embodiment of the present invention. It is a half cross-sectional view showing an example of the structure of the sealing unit according to the embodiment. It is explanatory drawing regarding the dimension of the sealing unit of FIG. It is an expanded cross-sectional schematic diagram of the boundary of a thin part and a boss part in an inner side connection position. It is a half cross-sectional view which shows the sealing unit before (a) and after (b) that a connection part expands toward a negative electrode terminal plate. 6 is a graph showing the relationship between explosion-proof operating pressure and φ1-φ2.

The alkaline dry battery according to the embodiment of the present invention includes a battery case having an opening, a power generation element housed in the battery case, and a sealing unit for sealing the opening of the battery case. The sealing unit includes a negative electrode terminal plate, a negative electrode current collector joined to the negative electrode terminal plate, and a gasket. The gasket includes a boss portion that penetrates the negative electrode current collector, an outer peripheral portion that contacts an end portion of the opening of the battery case, and a connecting portion that connects the boss portion and the outer peripheral portion. A thin-walled portion having an explosion-proof function is formed in an inner peripheral region adjacent to the boss portion of the connecting portion.

Here, the height H of the boss portion is 1.5 mm or more and 3.2 mm or less, and the first diameter φ1 of the circle drawn by the inner connecting position of the thin portion and the boss portion on the power generation element side, and the thin portion The difference between the boss and the boss and the second diameter φ2 of the circle drawn by the outer connecting position on the side of the negative electrode terminal plate: φ1-φ2 (hereinafter, the difference between the inner and outer diameters Δφ) is limited to 0.03 mm or more and 0.2 mm or less. ing.

By setting the height H of the boss portion to 3.2 mm or less, the volume of the entire gasket is reduced, so that more power generating elements can be accommodated in the battery case, and high capacity can be easily achieved. The height H of the boss portion may be 3.2 mm or less, but may be 3.0 mm or less, 2.5 mm or less, or 2.0 mm or less from the viewpoint of accommodating more power generating elements in the battery case. May be However, when the height H of the boss portion is smaller than 1.5 mm, the frictional force between the boss portion and the negative electrode current collector sharply decreases, and the boss portion easily moves to the negative electrode terminal plate side when the gasket softens. The space in which the connection part can expand can be too small. Therefore, the height H of the boss portion may be 1.5 mm or more.

Even when the height H of the boss portion is set to 1.5 mm or more, when the gasket softens, the movement of the boss portion toward the negative electrode terminal plate cannot be sufficiently suppressed, and the space for expanding the connecting portion becomes small. Sometimes. Even in such a case, by limiting the inner-outer diameter difference Δφ to 0.03 mm or more and 0.2 mm or less, the thin portion breaks when the connecting part swells appropriately or before the connecting part contacts the negative electrode terminal plate. become able to. Therefore, the explosion-proof operating pressure does not become too high, and a stable explosion-proof function can be obtained.

It is considered that when the inner-outer diameter difference Δφ is limited to 0.03 mm or more and 0.2 mm or less, the tensile stress when the connecting portion expands tends to concentrate on the boundary Cb between the thin portion and the boss portion at the inner connecting position. When the inner-outer diameter difference Δφ is less than 0.03 mm, the tensile stress is not sufficiently concentrated on the boundary Cb. Further, if the inner-outer diameter difference Δφ exceeds 0.2 mm, the explosion-proof operating pressure becomes too low, which may cause a problem of liquid leakage due to the explosion-proof operation.

When the boss has a sufficient height, the inner-outer diameter difference Δφ is usually designed to be almost 0 (zero). Even when considering the tolerance of the mold, Δφ is 0.02 mm or less at the maximum.

In the cross section of the gasket in the axial direction, the boundary Cb between the thin portion and the boss portion at the inner connecting position may not be chamfered. For example, the radius of curvature of the boundary Cb may be 0.1 mm or less. In this case, when the connecting portion expands, the tensile stress is more likely to concentrate on the boundary Cb, and the explosion-proof function is further stabilized.

Thermoplastic resin having heat resistance is used as the main component of the gasket. The main component means, for example, a material that occupies 90% by mass or more of the gasket. Specifically, a polyolefin resin such as polypropylene resin, a polyamide resin, or the like is preferably used as the main component of the gasket, but is not limited thereto. As the polyamide resin, for example, 6,6-nylon, 6,10-nylon, 6,12-nylon or the like is used. Of these, 6,10-nylon is preferable because it has an excellent balance between cost and liquid leakage resistance. Further, the gasket may contain a plasticizer, a heat stabilizer, an antioxidant, a lubricant, a filler, a coloring agent, a combustion inhibitor, etc., if necessary.

The alkaline dry battery according to the present embodiment can be suitably applied to, for example, a AAA battery. The smaller the size of the battery gasket, the higher the molding precision required for the thin portion. According to the present embodiment, it is possible to more easily manufacture a gasket having a stable explosion-proof function in a small size alkaline dry battery, so that it is easy to reduce the height of the boss portion of the gasket and to easily achieve high capacity.

The angle (hereinafter, skirt angle) θ on the power generation element side formed by the surface of the thin portion on the negative electrode terminal plate side and the height direction of the boss portion is preferably 45 degrees or more. The larger the skirt angle θ, the larger the resistance when the boss moves toward the negative electrode terminal plate side when the gasket is softened. The skirt angle θ is more preferably 50 degrees or more, and may be 90 degrees or more. However, from the viewpoint of stabilizing the explosion-proof function due to the thin portion of the gasket, the upper limit of the skirt angle θ is about 130 degrees, and preferably 120 degrees or less. If the skirt angle θ exceeds 130 degrees, it may be difficult to secure a space for the connecting portion to swell sufficiently.

The dimensions of the gasket may be obtained by, for example, taking a cross-sectional photograph of the sealing unit by a CT scan of the battery and measuring the dimensions, radius of curvature, angle, etc. of each part.

Embodiments of the present invention will be further described below with reference to the drawings, but the present invention is not limited to the following embodiments.

FIG. 1 is a half sectional view showing an example of the internal structure of an alkaline dry battery according to an embodiment of the present invention. FIG. 2 is a half sectional view showing the structure of the sealing unit according to the embodiment. A positive electrode 2 and a gelled negative electrode 3 are housed in a cylindrical battery case 1 having a bottom via a separator 4. The battery case 1 is obtained, for example, by pressing a nickel-plated steel plate into a predetermined shape. A conductive coating may be formed on the inner surface of the battery case 1.

The opening of the battery case 1 is sealed by a sealing unit 9 in which the negative electrode terminal plate 5, the negative electrode current collector 6, and the gasket 7 are integrally assembled. The negative electrode terminal plate 5 is obtained, for example, by pressing a nickel-plated steel plate or a tin-plated steel plate into a predetermined shape. A gas vent hole (not shown) is provided in the peripheral portion of the negative electrode terminal plate 5 for allowing gas to escape to the outside when the explosion-proof function of the thin portion 8 of the gasket 7 is activated. A flange portion 6 a is formed at an end of the negative electrode current collector 6, and the flange portion 6 a is welded to the negative electrode terminal plate 5. The negative electrode current collector 6 is obtained, for example, by pressing a brass wire rod into a nail shape having a predetermined size. The outer peripheral surface of the battery case 1 is covered with an exterior label 10.

The negative electrode current collector 6 penetrates the boss portion 7 a of the gasket 7. The outer peripheral portion 7b of the gasket 7 is in contact with the open end of the battery case 1 so as to be sandwiched therebetween, and is crimped to the peripheral edge of the negative electrode terminal plate 5. The annular connecting portion 7c that connects the boss portion 7a and the outer peripheral portion 7b has a thin portion 8 having an explosion-proof function in the inner peripheral region near the boss portion 7a. The minimum thickness of the thin portion 8 is set to, for example, 0.10 mm to 0.35 mm.

FIG. 3 is an explanatory diagram regarding dimensions of the sealing unit of FIG. 2. The height H of the boss portion 7a is set to 1.5 mm or more and 3.2 mm or less. The height of the boss portion 7a may be measured as the distance H between the upper and lower ends of the inner peripheral surface of the boss portion 7a that contacts the negative electrode current collector 6. The gasket 7 formed by resin injection molding may have an annular projection 7d formed on the inner peripheral edge of the end surface of the boss portion 7a due to the gate portion of the mold. In this case, the height excluding the annular protrusion 7d may be measured as the height H of the boss portion 7a.

In consideration of tolerance, a gap S may be formed between the end surface of the boss portion 7a on the negative electrode terminal plate 5 side and the flange portion 6a of the negative electrode current collector 6. The gap S contributes to ensuring a space in which the connecting portion 7c can expand. On the other hand, when the gasket 7 moves to the negative electrode terminal plate 5 side, the boss portion 7a may move a distance corresponding to the gap S and may be further deformed so as to cover the flange portion 6a.

The inner connecting position Cin between the thin portion 8 and the boss portion 7a on the power generating element side draws a substantially circular locus when viewed from the axial direction of the boss portion 7a. Similarly, the outer connection position Cout between the thin portion 8 and the boss portion 7a on the negative electrode terminal plate 5 side draws a substantially circular locus when viewed in the axial direction of the boss portion 7a. The difference between the first diameter φ1 of the circle drawn by the inner connecting position Cin and the second diameter φ2 of the circle drawn by the outer connecting position Cout: φ1-φ2 (that is, the inner-outer diameter difference Δφ) is 0.03 mm or more and 0.2 mm. Limited to:

FIG. 4 is an enlarged schematic sectional view of the boundary Cb between the thin portion 8 and the boss portion 7a at the inner connecting position Cin. In the cross section of the gasket 7 in the axial direction, the boundary Cb is not chamfered and has a sharply pointed acute angle shape. That is, the radius of curvature of the boundary Cb is sufficiently smaller than 0.1 mm. The skirt angle θ is in the range of 45 degrees or more and 90 degrees or less.

FIG. 5 is a half cross-sectional view showing a sealing unit before (a) and after (b) that the connecting portion 7c bulges toward the negative electrode terminal plate 5. When the battery is misused and the internal pressure of the battery rises, as shown in FIG. 5B, the thin portion 8 is broken while the connecting portion 7c bulges toward the negative electrode terminal plate 5, the internal pressure of the battery is released, and the safety is improved. Sex is secured. The pressure at which the thin portion 8 breaks is the explosion-proof operating pressure.

It is considered that the breakage of the thin portion 8 occurs from the boundary Cb as a starting point due to the concentration of stress on the boundary Cb shown in FIG. However, when the gasket 7 is softened due to the rise in the battery temperature, the softened boss portion 7a is pushed up to the negative electrode terminal plate 5 side as shown in FIG. And the negative electrode terminal plate 5 become closer, and the space in which the connecting portion 7c bulges toward the negative electrode terminal plate 5 becomes smaller. Therefore, if the explosion-proof operating pressure is not appropriate, it may be difficult to break the thin portion 8. On the other hand, when the inner-outer diameter difference Δφ is limited to 0.03 mm or more and 0.2 mm or less, the explosion-proof working pressure becomes appropriate, and when the connecting portion 7c swells to an appropriate degree, the connecting portion 7c becomes thin before contacting the negative electrode terminal plate 5. The part 8 comes to break.

The body diameter D of the negative electrode current collector 6 is preferably 2.0 mm or less, more preferably 1.8 mm or less. Further, from the viewpoint of ensuring excellent current collecting properties, the barrel diameter D of the negative electrode current collector 6 is preferably 1.1 mm or more, and more preferably 1.15 mm or more.

The surface roughness (R _max ) of the negative electrode current collector 6 may be 0.3 to 3.0 μm, for example. A plating layer of tin, indium or the like may be formed on the surface of the negative electrode current collector 6.

The negative electrode current collector 6 is made of brass, but the copper content of brass may be reduced. For example, when the copper content of brass is 50 to 60% by mass or less, the electric conductivity of the negative electrode current collector 6 is lowered, and the heat generation of the negative electrode current collector during misuse of the battery is increased. In such a case, the boss portion 7a easily moves to the negative electrode terminal plate 5 side, but since the explosion-proof operating pressure is appropriate, the explosion-proof function is stabilized.

A sealant may be interposed between the negative electrode current collector 6 and the boss portion 7a. The sealant makes it difficult for the alkaline electrolyte to leak from between the negative electrode current collector 6 and the boss 7a. As the sealant, a silicone resin, a fluororesin, a polyamidoamine-added epoxy resin, or the like can be used.

Although the type of the alkaline dry battery is not particularly limited, as described above, in the embodiment of the AAA battery, the effect of stabilizing the explosion-proof function by using the sealing unit becomes large.

Hereinafter, the specific configuration of the power generating element of the alkaline dry battery will be further described.
For the positive electrode 2, for example, a molded body of a mixture containing a positive electrode active material, a conductive agent and an alkaline electrolyte is used. A binder such as polyethylene powder and a lubricant such as stearate may be added to the mixture. As the positive electrode active material, manganese dioxide powder, nickel oxyhydroxide powder or the like is used. Graphite powder or the like is used as the conductive agent.

For the gelled negative electrode 3, for example, a mixture containing a negative electrode active material, an alkaline electrolyte, and a gelling agent is used. Zinc alloy powder is used as the negative electrode active material. Sodium polyacrylate or the like is used as the gelling agent. In order to improve the corrosion resistance of the zinc alloy, a metal compound having a high hydrogen overvoltage such as indium or bismuth or a surfactant may be added to the mixture.

For the separator 4, for example, a non-woven fabric mainly composed of polyvinyl alcohol fiber and rayon fiber is used.

Each of the positive electrode 2, the gelled negative electrode 3 and the separator 4 contains an alkaline electrolyte. As the alkaline electrolyte, for example, an aqueous solution containing 30 to 40% by mass of potassium hydroxide and 1 to 3% by mass of zinc oxide is used.

Hereinafter, the embodiments of the present invention will be further described based on examples, but the present invention is not limited to the examples. Here, a AAA alkaline dry battery having a structure as shown in FIG. 1 was produced.

<<Example 1>>
(1) Production of sealing unit A gasket 7 was produced by injection-molding 6,10-nylon into a predetermined shape using a plurality of types of molds. The height H of the boss portion 7a of the gasket 7 was 3 mm, the thickness of the thin portion 8 was 0.2 mm, and the inner and outer diameter difference Δφ was changed as shown in Table 1. When Δφ is a negative value, it means φ1<φ2. The skirt angle θ was set to 60 degrees. The radius of curvature of the boundary Cb between the thin portion 8 and the boss portion 7a at the inner connecting position Cin is sufficiently smaller than 0.1 mm.

A negative electrode current collector 6 was produced by processing brass having a copper content of 58 mass% into a nail shape having a total length of 30 mm and a body diameter of 1.20 mm. No plating layer was formed on the surface of the negative electrode current collector 6, and the surface roughness (R _max ) was 1.0 μm. On the other hand, a nickel-plated steel plate having a thickness of 0.4 mm was pressed into a predetermined shape to produce a negative electrode terminal plate 5, and the collar portion 6a of the negative electrode current collector 6 was welded to the negative electrode terminal plate 5. Then, the negative electrode current collector 6 was pressed into the hollow of the boss portion 7a of the gasket 7 to assemble the sealing unit 9.

(2) Preparation of positive electrode Electrolytic manganese dioxide powder having an average particle size of 35 μm and graphite powder having an average particle size of 15 μm were mixed at a mass ratio of 94:6, and 2 parts by mass of an alkaline electrolyte was added to 100 parts by mass of the mixture. Then, the mixture was sufficiently stirred and then compression-molded to obtain a flake-shaped positive electrode mixture. The flake-shaped positive electrode mixture was crushed into granules and then pressure-molded into hollow cylindrical pellets, and the obtained molded body was used as the positive electrode 2.

An aqueous solution containing 35% by mass of potassium hydroxide and 2% by mass of zinc oxide was used as the alkaline electrolyte.

(3) Preparation of Negative Electrode A gelling agent (sodium polyacrylate powder), an alkaline electrolyte, and a zinc alloy powder having an average particle diameter of 160 μm were mixed in a mass ratio of 0.8:33.6:65.6. Thus, a gelled negative electrode 3 was obtained.

(4) Assembly of Battery The positive electrode 2 was inserted into the battery case 1, and the positive electrode 2 was brought into close contact with the inner wall of the battery case 1 by a pressing jig. A bottomed cylindrical separator 4 was placed in the hollow of the positive electrode 2. For the separator 4, a non-woven fabric mainly composed of polyvinyl alcohol fiber and rayon fiber was used. After the alkaline electrolyte was injected into the separator 4 and a predetermined time elapsed, the gelled negative electrode 3 was filled in the separator 4. The outer peripheral portion of the gasket of the sealing unit was arranged in the vicinity of the opening of the battery case 1, and the opening end of the battery case 1 was bent inward and sealed to complete a AAA battery.

<Explosion-proof operation test>
Ten batteries each were prepared, a hole having a diameter of 4 mm was formed on the side surface of the battery case, water was injected from the hole to monitor the internal pressure, and the pressure at which the thin portion broke was determined as the explosion-proof working pressure. The results are shown in Table 1.

<Leakage test>
Ten of each battery was prepared and stored in an 80° C. constant temperature bath for 3 months, and the number of leaked batteries in 10 batteries was determined. The results are shown in Table 1.

FIG. 6 shows the relationship between the explosion-proof working pressure and the inner-outer diameter difference Δφ (φ1-φ2). It can be understood that when Δφ is less than 0.03 mm, the explosion-proof operating pressure becomes large and the explosion-proof function becomes extremely difficult to operate. Further, from Table 1, when Δφ exceeds 0.20 mm, the explosion-proof operating pressure slightly decreases but is within a range where there is no problem, but the explosion-proof function becomes too easy to operate and the probability of leaking increases. Can understand.

<<Example 2>>
A battery was manufactured in the same manner as in Example 1 except that the thickness of the thin portion 8 of the gasket 7 was 0.2 mm and the height H of the boss portion 7a and the inner/outer diameter difference Δφ were changed as shown in Table 2. ..

<Short circuit test>
Ten groups were produced by connecting four batteries in series. After storing 10 sets of batteries at 60° C. for 8 hours, they were left in a closed circuit state for 24 hours, then returned to an open circuit state and left for 1 week. Table 2 shows the proportion of the groups in which the explosion-proof function did not operate and any one of the four cells was damaged.

In addition, the elongation of the thin portion of the battery that was not damaged was measured, and the average value was measured. Specifically, first, a cross-sectional photograph is taken by CT scan of the battery before the connecting portion 7c before the short circuit test expands toward the negative electrode terminal plate 5, and the negative electrode of the connecting portion 7c shown in FIG. The length L of the XY line drawn by the surface on the terminal plate 5 side was determined. Next, for the battery after the short-circuit test in which the connecting portion 7c bulges toward the negative electrode terminal plate 5, similarly, a cross-sectional photograph is taken by CT scan, and the negative electrode terminal plate of the connecting portion 7c shown in FIG. 5B is taken. The length L′ of the X′-Y′ line drawn by the surface on the 5 side was obtained. Next, the average value (mm) of L'-L was obtained as elongation. The results are shown in Table 3.

First, if the height H of the boss portion exceeds 3.2 mm and becomes large, it is considered that the boss portion does not move in the first place, and even if Δφ is 0, the connecting portion is sufficiently expanded and the thin portion is broken. Therefore, the extension of the connecting portion 7c also increases to some extent. However, when Δφ becomes a negative value, the explosion-proof operating pressure becomes too large, so that the thin portion cannot be broken and the elongation of the connecting portion becomes significantly large.

Next, it can be understood that when the height of the boss portion is reduced and the Δφ is less than 0.03 mm, the probability of battery damage is high and the elongation of the connection portion is relatively large. On the other hand, by setting Δφ to be 0.03 mm or more, breakage of the battery is significantly suppressed and the elongation of the connecting portion is also small. This is because the explosion-proof operating pressure was appropriately reduced by setting Δφ to 0.03 mm or more. However, when the height of the boss portion is less than 1.5 mm, the battery is significantly damaged. It is considered that this is because the boss portion is likely to move to the negative electrode terminal plate side, and the space in which the connecting portion can expand becomes excessively small, so that the explosion-proof function does not operate.

INDUSTRIAL APPLICABILITY The alkaline dry battery according to the embodiment of the present invention is excellent in stability of the explosion-proof function and can have a high capacity, and thus is useful as a power source for various electronic devices.

1: Battery case, 2: Positive electrode, 3: Gelled negative electrode, 4: Separator, 5: Negative electrode terminal plate, 6: Negative electrode current collector, 6a: Collar part, 7: Gasket, 7a: Boss part, 7b: Outer peripheral part, 7c: connecting portion, 7d: annular protrusion, 8: thin portion, 9: sealing unit, 10: outer label, Cin: inner connecting position, Cout: outer connecting position, Cb: boundary, D: body diameter, S: gap

Claims (4)

A battery case having an opening,
A power generation element housed in the battery case,
A sealing unit for sealing the opening,
The sealing unit includes a negative electrode terminal plate, a negative electrode current collector joined to the negative electrode terminal plate, and a gasket,
The gasket includes a boss portion that penetrates the negative electrode current collector, an outer peripheral portion that contacts the opening end portion of the battery case, and a connecting portion that connects the boss portion and the outer peripheral portion,
An inner peripheral region of the connecting portion adjacent to the boss portion has a thin wall portion having an explosion-proof function,
The height of the boss portion is 1.5 mm or more and 3.2 mm or less,
A first diameter φ1 of a circle drawn by the inner connecting position of the thin portion and the boss portion on the power generating element side, and a first diameter φ1 of the circle drawn by the outer connecting position of the thin portion and the boss portion on the negative electrode terminal plate side. 2 Difference with diameter φ2: φ1-φ2 is 0.03 mm or more and 0.2 mm or less, alkaline dry battery. The alkaline dry battery according to claim 1, wherein a radius of curvature of a boundary between the thin portion and the boss portion at the inner connection position is 0.1 mm or less. The alkaline dry battery according to claim 1, wherein the gasket contains a polyamide resin. The alkaline dry battery according to claim 1, which is a AAA type.